Field of the Invention
The present invention relates to a method and apparatus for manufacturing a sheet, and more particularly, to a method and apparatus for manufacturing a sheet by a roll-to-roll process.
Description of Related Art
As display devices become thinner and lighter, glass substrates are also becoming thinner. In addition, displays having a curved surface instead of a planar surface are now being fabricated, and studies on flexible displays are also actively underway. Therefore, glass substrates are required to be thinner and more flexible.
When transporting or processing an ultra-thin glass sheet (having a thickness of 0.5 mm or less) as in the related art, the flexibility of glass makes it difficult to input the glass sheet into a processing line or transport the glass sheet along or out of the processing line. In addition, since respective sheets must be loaded one by one, productivity is still not optimized. In order to overcome this limited productivity and facilitate transportation, an approach of manufacturing a thin glass sheet by unwinding and transporting a thin glass web from a roll was introduced. The thin glass web or the thin glass sheet produced from the thin glass web can be used in a variety of fields, such as displays, electronic materials (e.g. photovoltaic cells, touch sensors and wafers), construction, and home appliances.
A web of a metal foil or a resin film is transported typically in a contact manner in a roll-to-roll process. In these fields, contact transportation does not create the problem of degraded surface quality. However, in the field of thin glass substrates that requires high surface quality, contact transportation may create severe problems, such as surface scratches, surface contamination caused by particles/organic matters, or breakage.
A method of coating a thin glass web with a protective film or a coating agent may be used in order to protect the glass surface. However, additional supplies must be continuously paid, which is problematic. In addition, a non-contact transportation approach using air floating was introduced in order to fundamentally remove factors damaging the glass substrate. However, the use of air also leads to the problem of utility costs. In addition, uncontrollable turbulence puts the web in an unstable state while being transported, thereby causing a dimensional defect when the web is cut into sheets.
When a web of film is transported, it is possible to control the transportation of the film web based on the elongation of the film since the film has a large elongation. However, the glass web tends to break when the transportation of the glass web is controlled based on the elongation of the glass since the glass has a small elongation. Therefore, it is impossible to use existing transportation apparatuses to transport the glass web.
The information disclosed in the Background of the Invention section is provided only for better understanding of the background of the invention and should not be taken as an acknowledgment or any form of suggestion that this information forms a prior art that would already be known to a person skilled in the art.